The invention relates to a method for measuring at least one physical magnitude, such as temperature, flow or pressure of the cooling fluid flowing in an individual cooling element circuit of a cooling element in a metallurgical furnace.
The invention also relates to an arrangement for measuring at least one physical magnitude, such as temperature, flow or pressure of the cooling fluid flowing in an individual cooling element circuit of a cooling element in a metallurgical furnace.
The invention deals with cooling in a liquid metallurgical process, in a metallurgical furnace such as a suspension smelting furnace, for example a flash smelting furnace, by a cooling system including several supply headers for distributing cooling fluid, such as cooling water, to the cooling element circuits of the cooling elements used for cooling a metallurgical furnace, said system also including several collection headers for collecting said cooling element cycles together. From one supply header, there is usually fed cooling fluid to the cooling element cycles of 10-20 separate cooling elements. One metallurgical furnace can include tens of such header units comprising a supply header and a collection header.
Liquid metallurgical processes create in the stationary structures surrounding the reaction space thermal stresses that fluctuate both locationwise and timewise. Owing to the combined effect of these stresses, an unbalanced temperature distribution is formed in the refractory lining structure, which phenomenon is undesirable for the total durability of the lining. The regular method in furnace cooling is to focus the cooling power in those areas of the furnace where the thermal stress caused by metallurgical reactions is high. For example in a flash smelting furnace, these areas are located in the lower part of the reaction shaft, as well as the settler walls and tap holes. The spreading and sizing the cooling power is based on theoretical calculations, modeling and experiences obtained from other similar furnaces. After the design step, the installed cooling elements used for cooling the lining are static coolers and do not actively react to the changes that take place in the process.
A time-bound balancing of the cooling process, together with balancing the thermal stress caused by the process, is achieved by controlling the rates of flow of the cooling water that carries the thermal energy away. Owing to local differences in the thermal stress, it is not sufficient to adjust the rates of flow header by header, but in order to ensure a balanced cooling area, it is necessary to manipulate individual element cycles, i.e. the cooling element cycles of individual cooling elements. Before manipulating the rates of flow, it is necessary to know the heat loss of each cooling element, but earlier the measuring thereof has been very expensive owing to the fact that each cooling element cycle has been provided with a an individual meter and cabling. Therefore said cost item has generally been totally left out of the overall investment and mere header specific measurement has been considered sufficient.
In case the heat loss transferred from the element by each cycle should be defined, it is necessary to know the cycle-specific temperature difference between the incoming and outflowing cooling water, as well as the rate of flow. The adding of a heat and flow meter in every cycle is, however, unnecessary, because the momentary return temperature and flow rate of each cooling element in the cycle does not represent very vital information for the process control. It is, however, needed for accurately defining the cooling element specific heat loss, but it suffices when the values are obtained a few times per hour, or when the degree of throttle in the supply water control valve is changed. Therefore a simultaneous measuring of all cycles is unnecessary, and the measuring operations can be carried out one at a time.